This invention relates generally to the manufacture of carbon electrodes used to form arcing devices comprising components of telephone protector modules and the like. More particularly, it relates to an improved method for impregnating the completed electrode to make it more resistive to deterioration, or dusting, during its useful life span.
The use of carbon electrodes to form arcing devices in telephone protector modules is well-known in the art. Most commonly, a pair of such electrodes are positioned in end to end relation to form a small gap there between. The electrodes become conductive upon the occurrence of excessive line voltages and currents which are caused to arc across the gap and thereby dissipate the excess currents to a source of ground potential. One electrode is positioned within a ceramic sleeve, an edge of which contacts the other electrode and thereby maintains a pre-determined gap. With each occurrence of arcing, a few carbon particles are loosened from the body of one or the other of the electrodes, which particles tend to gather in the gap and ultimately destroy the gap by filling the original interstice, thereby nullifying the protections offered by the device in which the carbons are incorporated. The useful life span of the carbon is thereby determined, to a substantial degree, by the ability of the carbon electrodes to maintain their structural integrity.
Where the electrodes are formed from carbon particles in an organic binder, the original molding process is not a completed operation. At a subsequent step, when the electrode is bonded to the ceramic sleeve which houses it, heat employed in bonding destroys the original organic binder, to produce an effect somewhat resembling that of a sintered metallic powder having many voids between the individual carbon particles. During the passage of arcing, particles disposed at or near the arcing surface are dislodged from the main body of the electrode, exposing adjacent particles which in turn are then loosened by subsequent arcing.